1. Field of the Invention
The present invention relates to a ceramic heater and more particularly to a ceramic heater mainly composed of silicon nitride and a method for producing it.
2. Description of the Prior Art
Conventionally, some metals and ceramics have been used as heating elements. Such metallic elements are nichromes and kanthals have such low thermal resistances that they readily deteriorate above 1,000.degree. C. Meanwhile, such ceramic elements as silicon carbide, molybdenum silicide and lanthanum chromite have low thermal shock resistances and strengths. In addition, it is difficult to use ceramic heating elements at a low voltage, for example, at 12 v of automotive batteries, because of their high specific electrical resistances.